The present application relates to a ferroelectric polymer memory device and a method for manufacturing such a device.
Ferroelectric memory based on ferroelectric polymers such as poly(vinyledene-difluoride) and its copolymers, is attracting much research interest. Though ferroelectric polymers exhibit much smaller remnant polarization compared to their inorganic counterparts, decent performances, simpler processing and significantly lower manufacturing costs have put ferroelectric polymer memory on the memory roadmap. The alleged demerits of having low remnant polarization can be overcome with proper design of the device configuration. For example, a greater overall response can be received by stacking memory cells to increase cell area.
Various methods of fabricating ferroelectric polymer memory devices with multi-stack or multi-layer configurations have been disclosed. One such fabrication method is described in U.S. Pat. No. 6,624,457, which discloses a method for fabricating a multi-rank, stacked polymer memory device. The method disclosed therein, however, requires repeated photolithography and is highly complicated. Another method of making a ferroelectric polymer memory device is disclosed in U.S. Pat. No. 6,858,862. The method disclosed therein, however, also requires repeated photolithography.
U.S. Pat. No. 7,084,446 discloses a polymer memory device comprising multi-layer memory stacks separated by insulating layers. Each multi-layer memory stack includes two layers of ferroelectric polymer material, each layer sandwiched between two sets of electrodes. Each multi-layer memory stack thus requires formation of three sets of electrodes. This adds to the manufacturing cost of the polymer memory device.
U.S. Patent Application Publication No. 2006/0048376A1 discloses a ferroelectric polymer memory having a plurality of stacked layers, each layer separated from an ensuing layer by a polyimide layer. The disclosed method employs a semiconductor substrate and requires patterning of metal electrodes by a reactive etching process. Further, because the polyimide layer completely segregates each memory stack from the next, each memory stack requires formation of two sets of electrodes. This adds to the manufacturing cost of the ferroelectric polymer memory.
Thus, there exists a need for a simple and inexpensive method of manufacturing a ferroelectric polymer memory device.